[Federal Register Volume 65, Number 61 (Wednesday, March 29, 2000)]
[Notices]
[Pages 16594-16598]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-7739]


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ENVIRONMENTAL PROTECTION AGENCY

[PF-928; FRL-6498-5]


Notice of Filing Pesticide Petition to Establish Tolerance for 
Certain Pesticide Chemicals in or on Food

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice.

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SUMMARY: This notice announces the intial filing of a pesticide 
petition proposing the establishment of regulations for residues of 
certain pesticide chemicals in or on various food commodities.

DATES: Comments, identified by docket control number PF-928, must be 
received on or before April 28, 2000.

ADDRESS: Comments may be submitted by mail, electronically, or in 
person. Please follow the detailed instructions for each method as 
provided in Unit I.C. of the SUPPLEMENTARY INFORMATION. To ensure 
proper receipt by EPA, it is imperative that you identify docket 
control number PF-928 in the subject line on the first page of your 
response.

FOR FURTHER INFORMATION CONTACT: By mail: James A. Tompkins, 
Registration Division (7505C), Office of Pesticide Programs, 
Environmental Protection Agency, Ariel Rios Bldg., 1200 Pennsylvania 
Ave., NW., Washington, DC 20460; telephone number: (703) 305-5697; e-
mail address: [email protected].

SUPPLEMENTARY INFORMATION:

I. General Information

A. Does this Action Apply to Me?

    You may be affected by this action if you are an agricultural 
producer, food manufacturer or pesticide manufacturer. Potentially 
affected categories and entities may include, but are not limited to:

 
------------------------------------------------------------------------
                                                          Examples of
           Categories                    NAICS            potentially
                                                       affected entities
------------------------------------------------------------------------
Industry                          111                 Crop production
                                  112                 Animal production
                                  311                 Food manufacturing
                                  32532               Pesticide
                                                       manufacturing
------------------------------------------------------------------------

    This listing is not intended to be exhaustive, but rather provides 
a guide for readers regarding entities likely to be affected by this 
action. Other types of entities not listed in the table could also be 
affected. The North American Industrial Classification System (NAICS) 
codes have been provided to assist you and others in determining 
whether or not this action might apply to certain entities. If you have 
questions regarding the applicability of this action to a particular 
entity, consult the person listed under FOR FURTHER INFORMATION 
CONTACT.

B. How Can I get Additional Information, Including Copies of this 
Document and Other Related Documents?

    1. Electronically. You may obtain electronic copies of this 
document, and certain other related documents that might be available 
electronically, from the EPA internet Home Page at http://www.epa.gov/. 
To access this document, on the Home Page select ``Laws and 
Regulations'' and then look up the entry for this document under the 
``Federal Register--Environmental Documents.'' You can also go directly 
to the Federal Register listings at http://www.epa.gov/fedrgstr/.
    2. In person. The Agency has established an official record for 
this action under docket control number PF-928. The official record 
consists of the documents specifically referenced in this action, any 
public comments received during an applicable comment period, and other 
information related to this action, including any information claimed 
as confidential business information (CBI). This official record 
includes the documents that are physically located in the docket, as 
well as the documents that are referenced in those documents. The 
public version of the official record, does not include any information 
claimed as CBI. The public version of the official record, which 
includes printed, paper versions of any electronic comments submitted 
during an applicable comment period, is available for inspection in the 
Public Information and Records Integrity Branch (PIRIB), Rm. 119, 
Crystal Mall #2, 1921 Jefferson Davis Highway, Arlington, VA, from 8:30 
a.m. to 4 p.m.,

[[Page 16595]]

Monday through Friday, excluding legal holidays. The PIRIB telephone 
number is (703) 305-5805.

C. How and to Whom Do I Submit Comments?

    You may submit comments through the mail, in person, or 
electronically. To ensure proper receipt by EPA, it is imperative that 
you identify docket control number PF-928 in the subject line on the 
first page of your response.
    1. By mail. Submit your comments to: Public Information and Records 
Integrity Branch (PIRIB), Information Resources and Services Division 
(7502C), Office of Pesticide Programs (OPP), Environmental Protection 
Agency, Ariel Rios Bldg., 1200 Pennsylvania Ave., NW., Washington, DC 
20460.
    2. In person or by courier. Deliver your comments to: Public 
Information and Records Integrity Branch (PIRIB), Information Resources 
and Services Division (7502C), Office of Pesticide Programs (OPP), 
Environmental Protection Agency, Rm. 119, Crystal Mall #2, 1921 
Jefferson Davis Highway, Arlington, VA. The PIRIB is open from 8:30 
a.m. to 4 p.m., Monday through Friday, excluding legal holidays. The 
PIRIB telephone number is (703) 305-5805.
    3. Electronically. You may submit your comments electronically by 
e-mail to: ``[email protected],'' or you can submit a computer disk as 
described above. Do not submit any information electronically that you 
consider to be CBI. Avoid the use of special characters and any form of 
encryption. Electronic submissions will be accepted in Wordperfect 6.1/
8.0 or ASCII file format. All comments in electronic form must be 
identified by docket control number PF-928. Electronic comments may 
also be filed online at many Federal Depository Libraries.

D. How Should I Handle CBI That I Want to Submit to the Agency?

    Do not submit any information electronically that you consider to 
be CBI. You may claim information that you submit to EPA in response to 
this document as CBI by marking any part or all of that information as 
CBI. Information so marked will not be disclosed except in accordance 
with procedures set forth in 40 CFR part 2. In addition to one complete 
version of the comment that includes any information claimed as CBI, a 
copy of the comment that does not contain the information claimed as 
CBI must be submitted for inclusion in the public version of the 
official record. Information not marked confidential wil be included in 
the public version of the official record without prior notice. If you 
have any questions about CBI or the procedures for claiming CBI, please 
consult the person identified under FOR FURTHER INFORMATION CONTACT.

E. What Should I Consider as I Prepare My Comments for EPA?

    You may find the following suggestions helpful for preparing your 
comments:
    1. Explain your views as clearly as possible.
    2. Describe any assumptions that you used.
    3. Provide copies of any technical information and/or data you used 
that support your views.
    4. If you estimate potential burden or costs, explain how you 
arrived at the estimate that you provide.
    5. Provide specific examples to illustrate your concerns.
    6. Make sure to submit your comments by the deadline in this 
notice.
    7. To ensure proper receipt by EPA, be sure to identify the docket 
control number assigned to this action in the subject line on the first 
page of your response. You may also provide the name, date, and Federal 
Register citation.

II. What Action is the Agency Taking?

    EPA has received a pesticide petition as follows proposing the 
establishment and/or amendment of regulations for residues of certain 
pesticide chemicals in or on various food commodities under section 408 
of the Federal Food, Drug, and Comestic Act (FFDCA), 21 U.S.C. 346a. 
EPA has determined that this petition contains data or information 
regarding the elements set forth in section 408(d)(2); however, EPA has 
not fully evaluated the sufficiency of the submitted data at this time 
or whether the data supports granting of the petition. Additional data 
may be needed before EPA rules on the petition.

List of Subjects

    Environmental protection, Agricultural commodities, Feed 
additivies, Food additives, Pesticides and pests, Reporting and 
recordkeeping requirements.

    Dated: March 24, 2000
James Jones
Director, Registration Division, Office of Pesticide Programs.

American Cyanamid Company

0F6088

Summary of Petition
    EPA has received a pesticide petition (0F6088) from American 
Cyanamid Company, P.O. Box 400, Princeton, NJ 08543-0400 proposing, 
pursuant to section 408(d) of the Federal Food, Drug, and Cosmetic Act 
(FFDCA), 21 U.S.C. 346a(d), to amend 40 CFR part 180 by establishing a 
tolerance for residues of the herbicide imazamox in or on the raw 
agricultural commodities alfalfa forage, seed and hay, canola seed, 
legume vegetable crop group and wheat forage, grain, bran, shorts, hay 
and straw at 2.0, 0.1, 4.0, 0.1, 0.1, 0.4, 0.3, 0.6, 0.6, 0.3, and 0.2 
parts per million (ppm), respectively. EPA has determined that the 
petition contains data or information regarding the elements set forth 
in section 408(d)(2) of the FFDCA; however, EPA has not fully evaluated 
the sufficiency of the submitted data at this time or whether the data 
support granting of the petition. Additional data may be needed before 
EPA rules on the petition.

A. Residue Chemistry

    1. Plant metabolism . The qualitative nature of the residues of 
imazamox (AC 299263) in soybeans, alfalfa, canola, peas, and wheat is 
adequately understood. The metabolism of imazamox has been studied in 
soybeans, peas, and canola. EPA has concluded that the nature of the 
residue is adequately understood and the residues of concern are the 
parent imazamox only. The metabolism of imazamox was also studied in 
wheat. EPA has concluded that the nature of the residue is adequately 
understood and the residues of concern are the parent imazamox, and the 
desmethyl, hydroxy-methyl metabolite CL 263284. The metabolism of 
imazamox was further studied in alfalfa. EPA has concluded that the 
nature of the residue is adequately understood and the residues of 
concern are the parent imazamox, metabolite CL 263284, the carboxylate 
of the CL 263284 metabolite, CL 312622 and the glucoside of the CL 
263284 metabolite, CL 189215.
    2. Analytical method. A practical analytical method for detecting 
and measuring levels of imazamox in soybean seed was submitted to and 
approved by EPA. This method (M 2248.01) is appropriate for enforcement 
purposes. A practical analytical method

[[Page 16596]]

for detecting and measuring levels of imazamox in canola seed was 
submitted to EPA. This method (M 3076) is appropriate for enforcement 
purposes. A practical analytical method for detecting and measuring 
levels of imazamox in legume vegetables (such as dry and succulent 
edible beans and peas) was submitted to EPA. This method (M 3076 with 
minor modifications) is appropriate for enforcement purposes. A 
practical analytical method for detecting and measuring levels of 
imazamox and its metabolite CL 263284 in wheat grain, forage, hay and 
straw was submitted to EPA. This method (M 3098) is appropriate for 
enforcement purposes. A practical analytical method for detecting and 
measuring levels of imazamox and its metabolites: CL 263284, its (CL 
263284) glucose conjugate (CL 189215), and the carboxylate of AC 263284 
(CL 312622) in alfalfa seed, forage and hay was submitted to EPA. This 
method (M 3178) is appropriate for enforcement purposes. All methods 
have undergone independent laboratory validation as required by PR 
Notices 88-5 and 96-1.
    3. Magnitude of residues--i. Magnitude of residues in crops--a. 
Soybeans, legume, vegetables and canola: No apparent residues of 
imazamox were observed in soybeans, dry or succulent peas, or dry or 
succulent beans, or canola at or above 0.05 ppm (the limit of 
quantification for the analytical methods). The field studies, 
conducted at 1- 5x the highest intended label use rate, clearly support 
the proposed tolerances of 0.1 ppm. The requirement for a soybean 
processing study was waived by EPA based on the results of field trials 
at rates up to 5x the maximum label rate. In these trials, there was no 
measurable residue of imazamox in soybean seed above the validated 
sensitivity of the method (0.05 ppm). In addition, results from the 
plant metabolism study showed no detectable residues of imazamox in oil 
obtained from soybean seed that had been treated at an exaggerated use 
rate.
    b. Wheat. A total of 20 field residue trials were conducted in 10 
different states. Applications in the trials were consistent with the 
proposed label directions for use. Analysis of the treated samples 
showed that the maximum imazamox plus its metabolite CL 253284 was 
under the proposed tolerances of 0.3 ppm in the grain, 0.4 ppm in the 
forage, 0.3 ppm in the hay and 0.2 ppm in straw at the proposed labeled 
pre-harvest intervals (PHI). Wheat grain for processing was obtained 
from a 5x-rate field study and samples were processed into bran, 
middling, shorts, flour and aspirated grain fractions. Analysis of the 
treated samples showed that the total residue of the imazamox parent 
and the metabolite CL 263284 concentrated in bran and shorts. The 
appropriate concentration factor for bran and shorts is 2x. The 
proposed tolerance for these two fractions is at 2x the tolerance for 
the proposed grain tolerance of 0.3 ppm or 0.6 ppm.
    c. Alfalfa. A total of 19 field residue trials were conducted in 12 
different states. Applications in the trials were consistent with the 
proposed label directions for use. Analysis of the treated samples 
showed that the maximum residues of imazamox plus its three metabolites 
(CL 263284, CL 263284 glucose conjugate metabolite CL 189215, and CL 
263284 carboxylate, CL312622) were under the proposed tolerances of 0.1 
ppm in the seed, 2.0 ppm in the forage and 4.0 ppm in the hay at the 
proposed labeled (PHI)
    ii. Magnitude of the residue in animals--a. Ruminants. The maximum 
dietary burden in beef and dairy cows results from a diet comprised of 
alfalfa hay and alfalfa forage for a total dietary burden that is 
significantly lower than levels that would require the proposal of 
tolerances in ruminants. This conclusion is based on exaggerated rate 
metabolism studies carried out on imazamox and its significant 
metabolites. Therefore, an exemption from tolerances in milk, meat and 
meat by-products under 40 CFR 180.6(a)(3) and (b) is proposed as it is 
not possible to establish with certainty whether finite residues will 
be incurred, but there is no reasonable expectation of finite residues.
    d. Poultry. The maximum poultry dietary burden results from a diet 
composed of alfalfa hay (meal) and wheat grain for a total dietary 
burden that is significantly lower than the levels that would require 
the proposal of tolerances in poultry. This conclusion is based on the 
exaggerated rate metabolism studies carried out on imazamox and its 
significant metabolites. Therefore, an exemption from tolerances in 
poultry meat, meat by-products, fat and eggs under 40 CFR 180.6(a)(3) 
and (b) is proposed as it is not possible to establish with certainty 
whether finite residues will be incurred, but there is no reasonable 
expectation of finite residues.

B. Toxicological Profile

    A complete battery of mammalian toxicity studies supports the 
tolerances for imazamox on soybeans and the rest of the legume 
vegetable crop grouping, canola, wheat and alfalfa. The data base is 
complete, valid and reliable, and all studies have been submitted to 
and approved by EPA. The toxicological data submitted to support the 
subject petition as amended include:
    1. Acute toxicity. Imazamox technical is considered to be nontoxic 
(Toxicity Category IV) to the rat by the oral route of exposure. In the 
acute oral toxicity study in rats, the LD50 value of 
imazamox technical was greater than 5,000 milligrams/kilograms body 
weight (mg/kg bwt) for males and females. The results from the acute 
dermal toxicity study in rabbits indicate that imazamox is slightly 
toxic (Toxicity Category III) to rabbits by the dermal route of 
exposure. The dermal LD50 value of imazamox technical was 
greater than 4,000 mg/kg bwt for both male and female rabbits. Imazamox 
technical is considered to be nontoxic (Toxicity Category IV) to the 
rat by the respiratory route of exposure. The 4-hour LC50 
value was greater than 6.3 mg/L (analytical) for both males and 
females. Imazamox technical was shown to be non-irritating to slightly 
irritating to rabbit skin (Toxicity Category IV). Based on the results 
of a dermal sensitization study (Buehler), imazamox technical is not 
considered a sensitizer in guinea pigs.
    2. Genotoxicty. Imazamox technical was tested in the following four 
assays measuring several different endpoints of potential genotoxicity. 
Collective results from these studies indicate that imazamox does not 
pose a mutagenic or genotoxic risk.
    i. Bacterial Mutagenicity assay - Negative.
    ii. In vitro structural chromosomal aberration assay - Negative.
    iii. In vitro CHO/HGPRT assay - Negative.
    iv. In vivo micronucleus aberration assay - Negative.
    3. Reproductive and developmental toxicity. The development 
toxicity study in rats conducted with imazamox technical showed no 
evidence of teratogenic effects in fetuses and no evidence of 
developmental toxicity. Thus, imazamox is neither a developmental 
toxicant nor a teratogen in the rat. The results from this study 
supported a no observed adverse effect level (NOAEL) for developmental 
toxicity of 1,000 mg/kg bwt day, the highest dose tested and limit 
dose. The NOAEL for maternal toxicity was 500 mg/kg bwt day, based on 
reduced mean body weights, weight gains and food consumption at 1,000 
mg/kg bwt day. Results from a developmental toxicity study in rabbits 
conducted with imazamox technical also indicated no evidence of 
teratogenicity or developmental toxicity. Thus, imazamox technical is 
neither a developmental toxicant nor a teratogen

[[Page 16597]]

in the rabbit. In the rabbit developmental toxicity study, the NOAEL 
for maternal toxicity was 300 mg/kg bwt day, based on decreased food 
consumption at 600 mg/kg bwt day, the next highest dose tested. The 
NOAEL for developmental toxicity was 900 mg/kg bwt day, the highest 
dose tested. The results from the two-generation reproduction toxicity 
study in rats with imazamox technical support a NOAEL for parental and 
reproductive toxicity of 20,000 ppm (or approximately 1,639 mg/kg bwt 
day, calculated from the food consumption data), the highest 
concentration tested. The NOAEL for growth and development of offspring 
is also 20,000 ppm (or approximately 1,639 mg/kg bwt day. Results from 
the reproduction study and the developmental toxicity studies conducted 
with imazamox technical show no increased sensitivity to developing 
offspring as compared to parental animals, because the NOAELs for 
growth and development of offspring were equal to or greater than the 
NOAELs for parental or maternal toxicity.
    4. Subchronic toxicity. No treatment-related adverse effects were 
noted in subchronic toxicity studies at the highest doses tested. A 
short-term (28-day) dermal study in rabbits was conducted with imazamox 
technical. No dermal irritation or systemic toxicity was observed at 
dose levels up to and including 1,000 mg/kg bwt day (highest dose 
tested), supporting a NOAEL of 1,000 mg/kg bwt day. In a subchronic 
(13-week) dietary toxicity study in rats with imazamox technical, no 
signs of systemic toxicity were noted, supporting a NOAEL of 20,000 ppm 
(or approximately 1,661 mg/kg bwt day, calculated from food consumption 
data), the highest concentration tested. In a subchronic (90-day) 
dietary toxicity study in dogs with imazamox technical, no signs of 
systemic toxicity were noted, supporting a NOAEL of 40,000 ppm (or 
approximately 1,368 mg/kg bwt day, calculated from the food consumption 
data), the highest concentration tested.
    5. Chronic toxicity. The low order of mammalian toxicity of 
imazamox technical is also evident from the chronic dietary toxicity 
studies. These studies showed no increased mortalities or clinical 
signs of toxicity attributed to imazamox treatment. Moreover, there 
were no treatment-related effects on food consumption, body weights, 
organ weights, or hematology, clinical chemistry, urinalysis or 
ophthalmologic parameters. There was no gross or microscopic evidence 
of treatment-related lesions or carcinogenicity in the three chronic 
studies conducted in dogs, mice, or rats.
    A 1-year dietary study was conducted with imazamox technical in 
dogs at dietary concentrations of 0, 1,000, 10,000, and 40,000 ppm. The 
NOAEL for this study was 40,000 ppm (or approximately 1,165 mg/kg bwt 
day, based on food consumption), the highest concentration tested.
    A chronic feeding/carcinogenicity study was conducted with imazamox 
technical in male and female rats at dietary concentrations of 0, 
1,000, 10,000, and 20,000 ppm. The NOAEL for systemic toxicity and 
carcinogenicity was 20,000 ppm (or approximately 1,167 mg/kg bwt day, 
based on food consumption) the highest concentration tested.
    A chronic feeding/carcinogenicity study was conducted with imazamox 
technical in male and female mice at dietary concentration of 500, 
3,500, and 7,000 ppm. The NOAEL for systemic toxicity and 
carcinogenicity was 7,000 ppm (or approximately 1,201 mg/kg bwt day, 
based on food consumption), the highest concentration tested.
    In the dietary exposure analysis for AC 299263 in/on Soybeans (PP 
6F4649) dated March 24, 1997, EPA determined that AC 299263 cancer 
classification is classified as not likely (to induce tumors in humans) 
according to the proposed new guidelines.
    6. Animal metabolism. The qualitative nature of the residues of 
imazamox and its metabolites CL 263284 and CL 263284 carboxylate CL 
312622 in animals is adequately understood. Based on metabolism studies 
with goats, hens and rats, there is no reasonable expectation that 
measurable imazamox-related residues will occur in meat, milk, poultry 
or eggs from the proposed use.
    7. Metabolite toxicology. No toxicologically significant 
metabolites were detected in plant or animal metabolism studies for 
soybeans or the rest of the crops in the legume vegetable crop 
grouping: (6) or canola. Therefore, no metabolites need to be regulated 
in these crops.
    The plant metabolism study in wheat indicated very low residues of 
concern. A very small amount of the metabolite CL 263284 was found in 
the wheat grain.
    The plant metabolism in alfalfa indicated very low residues in the 
alfalfa seed. However, the parent imazamox underwent metabolism to the 
metabolite CL 263284 (the same metabolite seen in wheat). This 
metabolite was captured by a glucose molecule to form the glucose 
conjugate CL 189215 and the hydroxymethyl AC 263284 was also further 
oxidized to the carboxylate metabolite CL 312622.
    Both metabolites, CL 263284 and CL 312622 were present in the rat 
metabolism study.
    No additional toxicologically significant metabolites were detected 
in any plant or animal studies.
    8. Endocrine disruption. Collective organ weight data and 
histopathological findings from the two-generation rat reproductive 
study, as well as from the sub-chronic and chronic toxicity studies 
conducted in two or more animal species, demonstrate no apparent 
estrogenic effects or effects on the endocrine system. There is no 
information available that suggests that imazamox would be associated 
with endocrine effects.

C. Aggregate Exposure

    1. Dietary exposure. The potential dietary exposure to imazamox has 
been calculated from the proposed tolerances for use on soybeans and 
other members of the legume vegetables crop grouping (6), canola, wheat 
and alfalfa. These very conservative chronic dietary exposure estimates 
used the tolerance value for all the raw agricultural commodities. In 
addition these estimates assume that 100% of the crops contain imazamox 
residues.
    i. Food. The Theoretical Maximum Residue Concentrations (TMRC) of 
imazamox on or in soybeans and other members of the legume vegetable 
crop grouping (6), canola, alfalfa, wheat grain, and its processed 
fractions are; 0.00577 mg/kg bwt day for the general U.S. population; 
0.000573 mg/kg bwt day for non-nursing infants; 0.001306 mg/kg bwt day 
for children 1 to 6 years of age; and 0.000887 mg/kg bwt day for 
children 7 to 12 years of age.
    ii. Drinking water. As a screening level assessment for aggregate 
exposure, EPA evaluates Drinking Water Level of Comparison (DWLOC), 
which is the maximum concentration of a chemical in drinking water that 
would be acceptable in light of total aggregate exposure to that 
chemical. Based on the chronic reference dose (RfD) of 3.0 mg/kg bwt 
day, determined by EPA, and the EPA's default factors for body weight 
and drinking water consumption, the DWLOCs have been calculated to 
assess the potential dietary exposure from residues of imazamox in 
water. For the adult population, the chronic DWLOC was 104,980 parts 
per billion (ppb), and for children, the DWLOC was estimated to be 
29,987 ppb.
    Chronic drinking water exposure analyses were calculated using EPA 
screening models (SCI-GROW for ground, water and GENEEC for surface

[[Page 16598]]

water). The calculated peak GENEEC value is 0.44 ppb and the SCI-GROW 
value is 0.055 ppb. For the U.S. adult population, the estimated 
exposures of imazamox residues in surface water and ground, water are 
approximately 0.0004% and 0.00005%, respectively, of the DWLOC. For 
children, the estimated exposures of imazamox residues in surface water 
and ground water are approximately 0.002% and 0.0002%, respectively of 
the DWLOC. Therefore, the exposures to drinking water from imazamox use 
are negligible.
    Based on the dietary and drinking water assessments, aggregate 
exposure to residues of imazamox in food and water can be considered to 
be negligible.
    2. Non-dietary exposure. There is no available information 
quantifying non-dietary exposure to imazamox. However, based on the 
physical and chemical characteristics of the compound, the proposed use 
pattern and available information concerning its environmental fate, 
non-dietary exposure is not expected.

D. Cumulative Effects

    Imazamox belongs to the imidazolinone class of compounds. The 
herbicidal activity of the imidazolinones is due to the inhibition of 
acetohydroxy acid synthase (AHAS), an enzyme only found in plants. AHAS 
is part of the biosynthetic pathway leading to the formation of 
branched chain amino acids. Animals lack AHAS and this biosynthetic 
pathway. This lack of AHAS contributes to the extremely low toxicity of 
imazamox in mammals. Although other registered imidazolinones have a 
similar herbicidal mode of action, there is no information available to 
suggest that these compounds exhibit a similar toxicity profile in the 
mammalian system. We are aware of no information to indicate or suggest 
that imazamox has any toxic effects on mammals that would be cumulative 
with those of any other chemical. Since imazamox is relatively non-
toxic, cumulative effects of residues of imazamox and other compounds 
are not anticipated. Therefore, for the purposes of this tolerance 
petition no assumption has been made with regard to cumulative exposure 
with other compounds having a common mode of herbicidal action.

E. Safety Determination

    1. U.S. population. Based on a RfD of 3.0 mg/kg bwt day determined 
from a NOAEL of 300 mg/kg bwt day, from the rabbit developmental 
toxicity study and a safety (uncertainty) factor of 100, the worse case 
estimate of chronic dietary exposure of imazamox from soybeans, the 
other members of the legume vegetable crop grouping (6), canola, wheat 
and alfalfa will utilize approximately 0.02% of the RfD for the general 
U.S. population. EPA generally has no concern for exposures below 100% 
of the RfD because the RfD represents the level at or below which daily 
aggregate dietary exposure over a lifetime will not pose appreciable 
risks to human health. The complete and reliable toxicity data and the 
conservative chronic exposure assumptions support the conclusion that 
there is a reasonable certainty of no harm from dietary (food) exposure 
to imazamox residues. Moreover, as exposure to residues of imazamox via 
water is negligible, there is a reasonable certainty of no harm from 
aggregate exposure to imazamox residues.
    2. Infants and children. The conservative estimates, as described 
above, indicate that dietary exposure of imazamox from soybeans, the 
other members of the legume vegetable crop grouping, canola, wheat and 
alfalfa will utilize: approximately 0.02% of the RfD for non-nursing 
infants; approximately 0.04% of the RfD for children ages 1 to 6; and 
approximately 0.03% of the RfD for children ages 7 to 12.
    No developmental, reproductive, or fetotoxic effects were noted at 
the highest doses of imazamox tested in guideline reproductive or 
developmental toxicity studies. The only maternal effects in the rat 
and rabbit teratology studies were decreased body weights, body weight 
gains and/or absolute and relative feed consumption in the higher dose 
groups of each study.
    Based on the current toxicological data requirements, the data base 
relative to prenatal and postnatal effects for children is complete, 
valid and reliable. Results from the teratology studies and the two-
generation reproduction study support NOAELs for fetal/developmental 
effects or reproductive/offspring effects, respectively, equivalent to 
the highest concentrations tested. As such, there is no increased 
sensitivity of infants and children to residues of imazamox. Therefore, 
an additional safety (uncertainty) factor is not warranted, and the RfD 
of 3.0 mg/kg bwt day, which utilizes a 100-fold safety factor, is 
appropriate to assure a reasonable certainty of no harm to infants and 
children.

F. International Tolerances

    There is no Codex Maximum Residue Level Established for Residues of 
Imazamox on any Crops.
[FR Doc. 00-7739 Filed 3-28-00; 8:45 am]
BILLING CODE 6560-50-F